This invention relates to magnetic recording media, and more particularly, to magnetic recording media having a magnetic layer in the form of a continuous thin film formed by the so-called oblique incidence evaporation process.
Among magnetic recording media for use in video, audio and other applications, active research and development works have been made on magnetic recording media, usually magnetic tapes having a magnetic layer in the form of a continuous thin film because of the compactness of a roll of tape.
The preferred magnetic layers for such continuous film type media are deposited films of Co, Co-Ni, and similar systems formed by the so-called oblique incidence evaporation process in which cobalt and optional elements are evaporated and directed to a substrate at a given angle with respect to the normal to the substrate because such evaporated films exhibit superior characteristics. The evaporated magnetic layers, however, have many disadvantages including insufficient bond between the magnetic layer and the substrate, high dynamic friction, poor travel, and inferior still performance in the still mode operation in video applications.
To obviate such shortcomings, magnetic layers are often formed in the presence of oxygen. The incorporation of oxygen contributes to some, but insufficient improvements in adhesion, dynamic friction, travel, and still performance. In addition, since magnetic characteristics and the above-mentioned characteristics are greatly changed with the amount of oxygen incorporated, it is difficult to control the factors to achieve a satisfactory compromise among these characteristics. The introduction of a considerable amount of oxygen into an evaporation equipment leads to additional disadvantages that the evaporation equipment must be more carefully operated and a molten evaporation source material is oxidized in a crucible.
It is also known to carry out a post-treatment on a magnetic layer to oxidize the magnetic layer surface. Dynamic friction is reduced while adhesion remains poor and still performance are insufficient.